text: #!/usr/bin/env python
  """
  Solution to Project Euler Problem 55
  http://projecteuler.net/
  
  by Apalala <apalala@gmail.com>
  (cc) Attribution-ShareAlike
  http://creativecommons.org/licenses/by-sa/3.0/
  
  Lychrel numbers
  
  If we take 47, reverse and add, 47 + 74 = 121, which is palindromic.
  
  Not all numbers produce palindromes so quickly. For example,
  
  349 + 943 = 1292,
  1292 + 2921 = 4213
  4213 + 3124 = 7337
  
  That is, 349 took three iterations to arrive at a palindrome.
  
  Although no one has proved it yet, it is thought that some numbers, like 196,
  never produce a palindrome. A number that never forms a palindrome through the
  reverse and add process is called a Lychrel number. Due to the theoretical
  nature of these numbers, and for the purpose of this problem, we shall assume
  that a number is Lychrel until proven otherwise. In addition you are given that
  for every number below ten-thousand, it will either (i) become a palindrome in
  less than fifty iterations, or, (ii) no one, with all the computing power that
  exists, has managed so far to map it to a palindrome. In fact, 10677 is the
  first number to be shown to require over fifty iterations before producing a
  palindrome: 4668731596684224866951378664 (53 iterations, 28-digits).
  
  Surprisingly, there are palindromic numbers that are themselves Lychrel numbers;
  the first example is 4994.
  
  How many Lychrel numbers are there below ten-thousand?
  """
  from palindromes import is_palindrome
  
  
  LIKELY_LYCHREL_ITERATIONS = 50
  
  
  def is_likely_lychrel(n):
      def reverse_int(n):
          return int(str(n)[::-1])
  
      for _ in range(LIKELY_LYCHREL_ITERATIONS):
          n = n + reverse_int(n)
          if is_palindrome(n):
              return False
      return True
  
  
  def count_likely_lychrels(upto):
      return sum(is_likely_lychrel(n) for n in range(1, upto))
  
  
  def test():
      assert not is_likely_lychrel(47)
      assert is_likely_lychrel(10677)
      assert is_likely_lychrel(4994)
  
  
  def run():
      assert 249 == count_likely_lychrels(upto=10000)
  
  
  if __name__ == "__main__":
      test()
      run()
  